Building on the past-life doctrines Hubbard first described in the 1950 bestseller Dianetics, which purported to teach techniques that could improve mental health, Hubbard created a universe populated with alien "Thetan" souls. (He later would reveal, in church materials that followers paid tens to hundreds of thousands of dollars to read, that the souls are really the ghosts of alien beings destroyed 75 million years ago by the evil galactic overlord Xenu.)

Although Hubbard was gaining groupies, not everyone bought into his new-found religion. Stern writes, journalist Russell Miller's 1987 biography, Bare-Faced Messiah, referred to Hubbard's Scientology: A History of Man as "possibly the most absurd book ever written," adding that "it was treated with great reverence by his followers."